REJUVENESCENCE IN NATURE. 151 



The ramification in 

 and Coleochcete pulvinata, exhibits similar characters. In 

 the last two examples there occurs, in addition, a descend- 

 ing ramification from the lower margin of the link-cells ; 

 so that, in many cases, an ascending branch springs 

 from the upper border, and a descending branch from 

 the lower border of the same cell. With the exception 

 of the reverse direction, the mode of origin of these 

 descending root-, or rather stolon-like branches, is the 

 same as that of the ascending. 



A further series of very varied organic differences next 

 arises in the relations of the cell-formation of the branches 

 to the cell-formation of the stem. If the cell-formation 

 in the branches is limited, and the branches fall short 

 considerably in size of the stem, they admit of comparison 

 with leaves. Thus, for example, in Draparnaldia, in 

 which the branches mostly arising in pairs from one cell of 

 the stem, as well as the branchlets of the second order 

 springing from these, are formed of much smaller cells 

 than the stem, the upper, larger, forming the hyaline 

 capillary points of the branches, while the lower and 

 shorter, abundantly furnished with green contents, pro- 

 duce within them the germ-cells. The large cells of the 

 stern of Draparnaldia are sterile vegetative-cells ; only 

 the apex of the long stem behaves in the same way as 

 the branches, and is, like them, fertile, and terminated by 

 a capillary point. In Batrachospermum, on the contrary, 

 the stern is unlimited in its growth, formed of a series of 

 link-cells, which originate through the repeated division 

 of a dome-shaped apical cell, and undergo no further 

 transverse division. From the upper border of the 

 young, still very short link-cells arise 5 6 radiately- 

 arranged projections, which are very early cut off, in the 

 shape of special cells, from the central cavity, which 

 remains as a link-cell, and these new cells then grow out, 

 by limited link-formation, into the small, again much 

 ramified branches, forming the peculiar globular whorls 



